Caprica, Syfy's dark, roiling prequel to Battlestar Galactica, is really about the American Empire and its unavoidable collapse, says actor James Marsters, who joins the show Friday. We took the opportunity to ask Marsters if he's coming back to Torchwood.

There are minor spoilers for Caprica in this post, by the way.

We were lucky enough to take part in a conference call with Marsters, best known for his role as Spike on Buffy and Angel, today. Marsters joins Caprica as Barnabus Greeley, the fanatical leader of a sect of monotheists linked to the train-bombers. The Chicago Tribune ran an exclusive clip the other day which showed Marsters' character wrapping his arms in barbed wire as a way of mortifying his flesh.

We asked Marsters how he felt about playing a religious zealot, after years of playing bad boys, and he said:

I love anybody who has conviction enough to make mistakes, because only people who make mistakes get into enough trouble to be called drama... I feel like I understand why he's doing what he's doing: he's living in a time that is coming apart at the seams. In his world, people are committing mass sacrifice, and mass execution, and mass orgies, and people are shooting each other for fun. In Rome, it was the coliseum. In Caprica, it's the V-club.

Even thought these virtual murders and orgies aren't real, Greeley sees them having a real psychological effect on people. And we find out that Greeley's own father was a decent, upstanding man until he became addicted to V-clubs, and now he's all but lost. So Greeley belives the polytheistic religions are not steering people towards moral behavior, and he wants to replace them with a monotheistic religion that has one God, and tells people what to do — with a clearcut punishment if you don't do it. "He's willing to have a revolution to make it happen," says Marsters.

And Marsters says Caprica's portrayal of a society on the verge of collapse — whose residents don't know they're doomed to destruction within 50 years — is a clear parallel to our own reality. "Being that Caprica is scifi, you don't have to call it America. You can call it Caprica." You only have to watch Battlestar Galactica to know how screwed these people are. Meanwhile, in the here and now, you only have to listen to climatologists or experts on food supplies and clean water to know how precarious our situation is.

"In scifi and fantasy, we address those issues," Marsters says. "We just change the names."

Marsters says he's filmed five episodes of Caprica so far, culminating in episode nine or ten, and he's not sure whether his character will reappear in the first season. "They've left the door open" to bring his character back.

He says Jane Espenson, whom he worked with on Buffy, really wanted him on the show and really fought for him, and he would follow Espenson anywhere. He originally auditioned for another role on Caprica, but even though he auditioned several times, it didn't work out. But when the Greeley role opened up, they thought of him. He hasn't gotten to hang out with Espenson this time around, but they've continued their relationship through her scripts and his acting. "I like to say we made love together, through the script and through the dailies [of his performance]. I tried to take everything she was adding, and make it just a little bit better."

We were dying to ask Marsters if he's had any chats with Russell T. Davies about coming back to Torchwood, where he plays Captain John Hart. There have been no discussions, he says, but Davies "knows I'm his bitch." Any time Davies wants to work with him, whether it's just five lines or the lead role, Marsters will be there. Likewise, someone asked Marsters about returning to Smallville, and he sounded up for it.

As for reprising his role as Spike, though, Marsters sounded dubious. Spike is supposed to be an immortal vampire who doesn't age. He doesn't want to have to explain away the fact that he looks older by with some "lame line" like saying that Spike has been drinking pig's blood and that's made him age slowly. But he still thinks that "when I'm rested, I look okay, with the right lighting." So he wouldn't say no to doing a screentest as Spike, to "see if we can light this guy" to look like he hasn't aged. "But I am aging, and I get nervous."